Electrical components, and electrical devices which include such components, exhibit electrical characteristics which are, to varying extents, temperature dependent. That is to say, such temperature dependency causes the components, and the electrical devices which include such components, to perform in manners dependent upon the ambient temperature levels about such components or devices.
For instance, impedance values of many electrical components, such as resistive elements, are directly related to the temperature levels of such components. A circuit including such resistive elements, constructed to be operable in a certain manner at a particular temperature might, at other temperature levels, exhibit altered operation. Analogously, transistor elements are also of characteristics which are temperature dependent. A circuit including such transistor elements might also exhibit altered operation at different temperature levels.
If the change in electrical characteristics is significant, operation of an electrical device including such components might be affected significantly as a result of temperature fluctuations. One manner by which to reduce the effects of temperature fluctuations upon the operation of an electrical device is to select the components thereof to be of constructions which exhibit reduced levels of variance as a result of changes in temperature. However, electrical components which exhibit reduced levels of variance due to temperature fluctuations are sometimes more expensive than their counterparts which exhibit greater levels of variance. And, in some instances, electrical components which exhibit characteristics which are relatively temperature invariant are simply not available.
Another manner by which to reduce the effects of temperature on the operation of an electrical device including such components is to maintain the electrical device in a temperature-controlled environment. By maintaining the electrical device in the controlled environment, changes in temperature of the electrical components do not occur, and the variance in operation of the electrical device is avoided.
A radio device is exemplary of a device which includes electrical components which exhibit characteristics which are temperature-dependent. For instance, a radio transmitter operable to transmit radio signals is a device whose operation is affected by the ambient temperature levels at which the radio transmitter is operated. That is to say, when the radio transmitter is operated at different temperature levels, the characteristics exhibited by the components thereof affect operation of the transmitter. A radio signal intended to be transmitted at a selected frequency might instead be transmitted at a frequency other than that which is intended. Analogously, a radio receiver is also constructed typically of electrical components which exhibit characteristics dependent upon the temperature level. A radio receiver, tuned to a particular frequency to receive a receive signal might, due to temperature variations, be tuned to a frequency other than that which is intended. An intended receive signal might thereby not be detected by the radio receiver.
While changes in temperature might result in misoperation of the radio receiver, thereby preventing adequate reception of radio signals transmitted thereto, such temperature changes resulting in misoperation of a radio transmitter can further result in interference in the proper operation of other radio receiver devices. That is to say, if misoperation of the radio transmitter causes radio signals to be generated upon radio channels other than the intended channel, such radio signals might interfere with signal reception by other radio receivers.
A cellular communication system includes both radio receivers and radio transmitters. A cellular system typically includes a plurality of spaced-apart base stations, each base station formed of a radio transceiver having both radio transmitter circuitry and radio receiver circuitry. A portion of the electromagnetic spectrum is allocated to a cellular communication system to permit the communication of radio-frequency signals between a base station and mobile stations positioned throughout a geographical area encompassed by the network infrastructure of the system. The spectrum allocated to the cellular communication system is efficiently utilized as relatively low-power signals are generated by the mobile stations and network infrastructure so as to permit re-use of the same frequency channels at different locations throughout the area encompassed by the cellular communication system.
The radio transceivers forming the base stations are typically housed within enclosures, herein referred to as cabinets, to shield the circuitry of such radio transceivers from environmental conditions. But, the ambient temperature levels within such cabinets are susceptible to variation as a result of changes in the ambient temperature levels. Such temperature variations make the radio transmitter and receiver circuitry of the base stations susceptible to misoperation for reasons as noted above. While heating elements can be positioned within the cabinets containing the radio transceiver circuitry, such heating elements increase the cost of the base stations as well as require the cabinets to be of increased dimensions.
A manner by which to maintain the temperature levels about the radio transceiver circuitry without utilizing separate heating elements would advantageously reduce the costs associated with the base stations while also permitting the cabinets in which such transceiver circuitry is positioned to be reduced, all the while ensuring that operation of the radio transceiver circuitry not be adversely affected as a result of ambient temperature fluctuation.
It is in light of this background information related to the affects of temperature fluctuations on the operation of electrical devices that the significant improvements of the present invention have evolved.